The following patents and patent applications are herein incorporated by reference: U.S. Pat. No. 4,126,854 to Sheridon; U.S. Pat. No. 4,143,103 to Sheridon; U.S. Pat. No. 5,604,027 to Sheridon; pending U.S. Pat. application Ser. No. 08/960,865 entitles xe2x80x9cTWISTING CYLINDER DISPLAYxe2x80x9d filed Oct. 30, 1997; and pending U.S. Pat. application Ser. No. 08/960,868 entitled xe2x80x9cA TWISTING CYLINDER DISPLAY USING MULTIPLE CHROMATIC VALUESxe2x80x9d filed Oct. 30, 1997; U.S. Pat. application Ser. No. 08/713,935, entitled xe2x80x9cMONOLAYER GYRICON DISPLAYxe2x80x9d; U.S. Pat. application Ser. No. 08/713,936, entitled xe2x80x9cHIGH REFLECTANCE CYRICON DISPLAYxe2x80x9d; U.S. Pat. application Ser. No. 08/716,675, entitled xe2x80x9cGYRICON DISPLAY WITH INTERSTITIALLY PACKED PARTICLE ARRAYSxe2x80x9d; and U.S. Pat. application Ser. No. 08/713,325, entitled xe2x80x9cGYRICON DISPLAY WITH NO ELASTOMER SUBSTRATExe2x80x9d.
1. Field of the Invention
The invention relates to visual displays. More particularly, the invention relates to reusable, paper-like, gyricon or twisting-particle type or other bistable visual displays and apparatus for driving displays.
2. Description of Related Art
Paper is a preferred medium to present and display text and images. A reason for paper being a preferred medium is the many advantages that are realized with the use of paper as a display medium. For example, paper is thin, lightweight, portable, flexible, foldable, cost efficient, high contrast, reusable, basically permanent, and can easily be configured into a multitude of shapes. In addition, paper does not have any limitations on size, other than practicability, and as such, can be used as display media such as, for example, sticky notes or such, maps and billboards, to name a few. Furthermore, paper is capable of maintaining a displayed image without the need for a power source, such as, for example, batteries and other such stored energy sources. In addition, paper can be read in ambient light, as well as marked upon with any number of implements, such as, for example, a pen, pencil, paintbrush, printers, photocopiers, and the like.
However, although paper has many advantages as a display medium, paper is not well suited for real-time display purposes. Real-time imagery from computer, video, and other sources cannot be displayed by means other than, for example, a cathode-ray tube (CRT) display or a liquid-crystal display (LCD). Unfortunately, most real-time display media lack many of the desirable advantages of paper, such as, for example, being lightweight, thin, portable, physical flexibility, and the ability to retain a displayed image in a stable manner without a power source. As such, attempts have been made to combine the desirable qualities of paper with those of real-time display media in order to provide a display that offers the best of both worlds. One such display is electric paper.
Like paper, electric paper can be written on and erased, can be read in ambient light, and can retain information in the absence of an electric field or other external retaining force. Also, like ordinary paper, electric paper can be made in the form of a lightweight, flexible, durable sheet that can be folded or rolled into tubular form about any axis and conveniently placed into a shirt or coat pocket, and then later retrieved, restraightened and read substantially without loss of information. Yet, unlike paper, electric paper possible can be used to display imagery in motion. Thus, electric paper is adaptable for use in computer systems, television, signs and a host of other application within office, industrial and domestic settings.
A gyricon display, also called a twisting-element display, rotary element display, particle display, dipolar particle light valve, etc., offers an example of a technology for making a form of electric paper. Briefly, a gyricon display is an addressable display made up of a multiplicity of optically anisotropic particles, such as, for example, spheres, each of which can be selectively rotated to present a desired image to an observer. For example, a gyricon display can incorporate rotational elements each having two distinct halves, e.g., one half may be black, while the other half is white.
The rotational elements are embedded in a sheet of optically transparent material that contains a multiplicity of cavities and is permeated by a transparent dielectric fluid. The fluid-filed cavities accommodate the rotational elements, one element per cavity, so as to prevent the elements from migrating within the sheet. Each element has a distinct electrical characteristic so that the elements are electrically as well as optically anisotropic Thus, an element can be selectively rotated within in respective cavity by application of an electric field, so as to present either the black or the white half to an observer viewing the surface of the sheet, for example.
The electric field is applied to the sheet by an external power source that is coupled across electrodes within the sheet. The polarity of the applied electric field dictates which portion of the elements is viewable to an observer. For example, a positive electric field may cause the elements to rotate such that block portions of the elements are visible, whereas a negative electric field may cause the elements to rotate so that white portions of the elements are visible. Thus, an electric field that is applied with alternating polarities can result in a switching or flashing display. However, the known gyricon displays cannot switch without the external power supply coupled across the electrical conductors within the sheet.
The invention provides a display in which the display is powered by ambient energy. The invention includes a controller that provides a signal for driving the display, which may have a large surface area, using only ambient energy. The controller can apply the driving signal to the display using only ambient energy because the optically anisotropic particles require very little energy to rotate. In other words, the display is a stand alone display with no external power source, such as batteries, attached to the display to provide the power needed for the application of the electric field necessary to drive the display.
In another aspect of the invention, the display is switchable display that is both powered by and viewable in ambient energy, e.g., visible light. The switchable display oscillates or alternates the presentation of the display. For example, the display is switched from a black-on-white display to a white-on-black display.
In another aspect of the invention, the display is a bistable display that is powered by and viewable in ambient energy or light. The display is bistable because the image presented by the display is maintained when there is no power or their driving signal applied to the display.
In yet another aspect of the invention, a conductor pattern may be applied to the back of the display to form a user customizable display. The conductor pattern may be manually applied by the user, e.g., metallic foil letters or symbols can be adhered to the display, or may even be printed by a printer using a conductive liquid as desired by the user.
The invention also provides circuitry for driving a display based on ambient energy.
These and other aspects of the invention will be described in or be apparent from the following description of specific embodiments.